This invention relates to a hydraulic circuit having dual cylinders and more particularly to a hydraulic circuit wherein the dual cylinders are controlled with a single joystick that is movable in a manner that is intuitive to the operator.
Many machines have work elements that are controlled by a single joystick controller. Likewise, several machines have work elements wherein the up and down movement thereof is controlled by independent dual hydraulic cylinders. The joystick controllers may produce electrical signals to control a main control valve or may result in the actuation of hydraulic pilot valves which in turn hydraulically operate a main control valve. In current joystick controllers, the directional movement of the single joystick""s motion does not correspond to the independent directional movement of the respective right and left cylinders. A typical pilot control arrangement is illustrated U.S. Pat. No. 5,063,739 issued Nov. 12, 1991 to Caterpillar Inc. and illustrates pilot controls 23,24 that could be one integral joystick controller. It is desirable for the operator to move the joystick lever in a direction that would intuitively result in the left and right hydraulic cylinders moving in a corresponding direction. For example, if the operator moves the joystick control lever forward, the operator would want the implement to move down and if the operator moves the lever rearward, the operator would want the implement to move up. Additionally, the operator would also want to move each cylinder independently so that the implement can be oriented in various positions. With the past joystick controllers, the movement of the implement does not correspond to the instinctive or intuitive movement of the operator.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the present invention, a hydraulic circuit is provided to intuitively control the movement of first and second hydraulic actuators. The hydraulic circuit includes a source of pressurized fluid, a reservoir, a first main control valve connected between the source of pressurized fluid and the first hydraulic actuator, and a second main control valve connected between the source of pressurized fluid and the second hydraulic actuator. A joystick controller having a control lever is provided in the circuit and is connected to the first and second main control valves. The joystick controller is operative to actuate the respective first and second main control valves in response to movement of the control lever of the joystick controller. The control lever is movable through a full circular pattern to actuate the respective first and second main control valves. A reference axis is defined in the joystick controller and oriented at a perpendicular position relative to the operator. Movement of the control lever along a path forty-five degrees of the reference axis results in a single control signal being directed to one end of one of the respective first and second main control valves. Movement of the control lever in a path less than forty five degrees results in two separate signals being directed to opposite ends of one of the first and second main control valves. Movement of the control lever along a path greater than forty five degrees results in two separate signals being directed to corresponding ends of each of the first and second main control valves.
In another aspect of the present invention, a method provides intuitive movement of a pair of hydraulic cylinders in a hydraulic circuit by operator movement of a control lever of a joystick controller having a reference axis and is operative to control actuation of first and second main control valves. The method includes the steps of orienting the reference axis perpendicular to the position of the operator, generating a single control signal from the joystick controller in response to movement of the control lever along a path oriented at forty five degrees relative to the reference axis, generating two separate control signals from the joystick controller and directing the respective signals to corresponding ends of each of the first and second main control valves in response to the control lever being moved in a path greater than forty five degrees of the reference axis, and generating two separate control signals from the joystick controller and directing the respective signals to opposite ends of one of the first and second control valves in response to the control lever being moved in a path less than forty five degrees of the reference axis.